The present invention relates to a pattern recognition device and, particularly, to such device suitable for use in detecting an object and/or defects thereof to be recognized on the basis of video signals corresponding to an image of the object obtained by a video camera.
In an example of a conventional pattern recognition device disclosed in Japanese Patent Application Laid-Open No. 60-39581, a detection of abnormal operation of an injection mold machine in its injection molding cycle or a test of printed circuit boards during manufacturing steps thereof is performed on a video image of a metal mold and its periphery or a printed circuit board itself on such as a display screen PIC shown in FIG. 10 of this application. That is, the detection or test is performed on the basis of a decision of whether or not a predetermined variation occurs in the video signal.
In such a conventional system, each of a plurality of monitor regions Kj having common shape and size and including a plurality of monitor points is set with respect to a predetermined one (Pj) of the monitor points and superimposed on an image of the object on the PIC screen and monitor information concerning the luminance of the monitor region Kj is obtained every process cycle by integrating video signal portions obtained at the monitor points, where j is a positive integer. Then, an abnormality of the monitor region of the object is detected when unexpected variation occurs in the monitor information during each process cycle.
In such a system, when a position of an image on the display screen PIC is changed by any unintended positional deviation of the object with respect to the video camera or any unintended change of an angle of the camera, a position Pj(xj, yj) of the predetermined monitor point Pj with respect to which the monitor region Kj is set is changed, resulting in an error.
As shown in FIG. 11, in the case of testing of a printed circuit board, for example, a video signal VD is obtained by a video camera 2 disposed in a facing relation to a surface of a printed circuit board 1 mounted in a position determined by a field of sight FILD of the video camera. It has been known, however, that it is very difficult to precisely mount a number of printed circuit boards 1 in an area of the field FILD of the video camera 2 without troublesome procedures and, therefore, a parallel positional deviation of the image of the printed circuit boards in any direction within the display screen PIC is unavoidable in practical applications.
In an object recognition device for use in a monitoring device of an injection mold machine, in order to obtain a video image of a movable half 5 of a metal mold and its holder 6 by a video camera 7 having a field of sight FILD when the movable mold half 5, together with the holder 6, is opened with respect to a fixed half 8 of the metal mold and its holder 9, the video camera 7 is mounted on the fixed mold half 8 through a mounting 10 so that it can look down on the movable mold half 5 and its peripheral portion obliquely, as shown in FIG. 12.
In this case, when the mounting position of the movable mold half 5 is slightly deviated or the angle of the video camera 7 is slightly changed from a predetermined set position, a deviation of an image of the movable mold half on the display PIC is unavoidable. In such case, troublesome correction procedures are required to correct deviation.
In order to solve this problem, it may be considered to move each monitor region Kj on the display PIC in parallel in a direction and by a distance corresponding to those of the image deviation, respectively. This procedure is very difficult and the difficulty is amplified when the number of monitor regions is large.